A Single Stroke of Hell
by Vacarria
Summary: Mercury knew that Cinder was- no, is a genius for her plan in infiltrating Beacon and destroying it in one swoop. That included his 'staged' Finals fight with Yang Xiao Long. But the thing is... a single decision to change the roulette's outcome would be the end to their hard-earned infiltrated stay in Beacon. And a man turned demon would be the one to do so. Oneshot.
1. Chapter 1

_All according to plan._

Cinder was- no, _is a genius_. Then again, that 'genius' was contributed alongside a few other variables. Hell, they managed to come in deep within the tourney without arousing anyone's attention. Despite those claims of 'high security', they sneak past it. And that's without abusing the illusions that Emerald had. The only thing left for him was to do his act and everyone's going to be awry. The target they wanted is already in their reach, well within the hacking they induced in the CCT Tower.

He smirked lightly, knowing that his job is still not over. He has yet to fight Yang Xiao Long, the near-tempered blonde of Team RWBY. Her inexperience alone was enough to be fooled by Emerald's abilities. And Oum bless her for the numerous times it saved him. Well, almost.

Mercury Black continued to ponder as the podium murmured about the upcoming finals. Well, as if he can't wait as well to see the look in her eyes. He along with the remaining teams of one stood in the center of the floating Amity Colosseum, waiting for the technobabble from the commentators to die down. Just as the annoying commentators, Port and Oobleck, finished stating the rules of the finals, the roulette started. What they don't know is that Cinder's side is the one deciding who would fights who. Victory is in their grasps.

By then, the roulette started, with the first fighter being Mercury. Just as planned.

The ones who have yet to fight move away from the platform, waiting outside of the octagonal battlefield for them to be picked.

The second roulette ended. Yang Xiao Long's face pasted on the screen.

 _'Bingo.'_

 **"Ehem, ehem."**

The raven-haired fighter could only ponder as the commentators start to talk again, interrupting the process. The voice was apparently from Port himself.

 **"Looks like we have some 'technical' issues. Apparently, the roulette should've stopped a second before and continued."**

What.

Oobleck's fake cough filled the colosseum, **"The roulette will be rolled back a little to decide our fighter for Mercury Black. Sorry, young one, but process is process."**

Out of all days too! It had to be a malfunction. He sighed, but he still knew what to do. As long as manages to provoke his opponent when he's already down, his job would be complete. Sadly, it can't be Xiao Long, but it can't be helped either. The roulette rolled back a bit to where it should've stopped, and it stopped.

It stopped at a black-haired teenager without somewhat a classy uniform. Touche.

 **"Kurogane Ikki."**

Mistral name. Mistral fighting. It's bound to be ugly, but who can blame him. If he's worth a fight, then he's worth the effort.

Mercury could only stare at the uniformed teenager as he entered the platform, before it suddenly rose from the ground for almost five meters. He look unarmed for all he cared, and he was someone whom Cinder didn't have info of. He was a complete blank in their entry. Just like his three other companions. But one thing remains the same, he is Mistralian and that alone makes him a threat.

The uniformed teenager, Ikki, opened his mouth.

"To be honest, I'm kind of thrilled to fight someone of your caliber."

What a surprise. A nerd.

"Well, people do like my suave. And seriously," Mercury brushed off his shoulder, "you talk to your opponents that much before a fight?"

Ikki could only laugh a bit and close his eyes, hinting his amusement.

"It's becoming a quirk of mine. Anyway, the pleasure's mine to fight you," he bowed, just before getting into a stance.

"Also," Mercury pointed at his hands, "where's your sword?"

Ikki raised his brow, "Oh, my sword? Don't worry."

...

...

...

" _It's with me_."

Mercury could only raise his brow in confusion, as the sudden ascension of the platform came to a halt along with the ring of stoplights shining above them.

Seriously, he fought all those matches with a sword and say that even without it, he still has it? What kind of sword code does he follow?

"I assume that you're confused, right?"

Mercury was for all he cared.

"Don't worry, I'll show it now."

The grey-haired fighter dropped his jaw as a faint light radiated from his open right hand. Just as parts of dirt and dust swelled in the glowing light, he clenched his fist and slammed it sideways to his other clenched fist. The result was a radiating light that give shape to what might be his own weapon.

"Intetsu!"

He commanded, forming a sword out of damn nowhere.

The black samurai sword was different from Yatsuhashi behemoth of a blade, even if the blade was near Yatsuhashi's blade's size. It had serrated edges that gleam sharpness through the poignant blade, its curved edge giving it a large demeanor as Ikki stood into position, pointing the blade's end to Mercury's neck. For the first time, he hadn't seen such stance except from some notable figures. But the fighting position that he took screamed Mistralian.

Mercury shrugged off the thought as he took his stance, his right arm forward and facing his opponent. A moment later, the timer started.

 _"Three."_

Mercury slowly paced to Ikki's position, never leaving his stance.

 _"Two."_

Ikki tightened his grip and his glare more subtle than it should be.

 _"One."_

Mercury stopped for about a meter away from the single-edged blade.

Then silenced followed, as the final announcement starts.

 _ **"Begin!"**_

Mercury gave the first strike as he kicked towards Ikki's feet, only for it to be blocked by his sword. He then followed it up with another kick from his left foot. As soon as the two soles of his feet meet his face, he fired shots from his weaponized leg.

That tactic soon failed as the next thing Ikki did, before the shots connected, was toppling him to the ground with his right hand. Just as Mercury's face hit the ground, a slash followed. Instead, Mercury raised his legs and pointed the soles at his face again. But before that would happened again, the raven-haired student jumped back.

Mercury, without him taking up his space, stood up and regained his posture.

 _'Damn, as if he's reading my every move!'_

The next medley of kicks and slashes soon followed. Mercury, without skipping a beat, saw an opening and followed his kick with another one. The raven-haired student couldn't block it with his blade without getting hit by the other foot.

Instead, he blocked it with the blade's hilt.

Mercury was starstruck as he was pushed aside and with Ikki getting a decisive slash to his abdomen. The fighter couldn't believe it, even no one in Mistral does that! His thoughts, however, were stopped as Ikki continued the assault. Those thoughts alone made him nerve wracked as he couldn't find an opening. Even if he decides to make him lose his guard, he follows it up with another move. As if he could read his distorted mind.

The grey-haired fighter shrugged it off. He was getting too predictable if he's thinking like this.

Just as his other kick got blocked by Ikki's Intetsu, he placed both feet on the blade and shot at him. Using the momentum, he created a wide space for him to throw a barrage as he saw the raven-haired student somewhat disoriented from blow. However, he was only dazed for a moment and after a shrug, rushed towards Mercury.

The fighter decided to take aim as he fired several shots from his feet, aiming his kicks to the air towards where Ikki was. A smirk followed as he saw Ikki's face nearly in contact with his shot.

And a frown as his body disappeared and reappeared behind the shot.

The fighter panicked by his sudden 'teleportation'. He then fired several shots, only for the swordsman to dodge it seamlessly. The crowd was somewhat confused as well, of course, but none of it mattered for Mercury's distress towards his opponent.

 _'Emerald, what the hell!? Help me!'_

He could only look at the green-haired assassin sitting and watching from the seats with a furious glare as the swordsman threw another barrage when he was in range. Mercury continued to defend from his assault, dodging and blocking from the blade's edge. He then noticed something floating behind Ikki's back. It was Emerald's signal, using her power, to tell him of the next move that she would hallucinate.

Mercury smirked as he would see what the swordsman would do. Instead of stopping, he slashed at him.

"W-what?!"

Even Emerald, who wasn't in the fight, had her eyes wide open. Instead of stopping to see the hallucination of several Mercurys, he instead slashed directly at his real body. Mercury jumped back as the swordsman took back his composure, going into his stance.

"I know that it's not your power," he pointed his blade at the fighter.

Normally, he would bluff, but it wasn't. He managed to figure it something was wrong, and tell him that it wasn't even his power. And that was during the span of the fight. How the hell?!

"To be honest, the other teams would've won without that power. I noticed it quickly when all of them started shooting at nothing. And all of that happened when they battled against you and your team."

Mercury gritted his teeth.

"But that doesn't matter," and that alone made Mercury and the crowd look at him.

Mercury could only scream in anger as he rushed at the swordsman. Emerald's power be damned, he already knows his next move! Unless...

The fighter continued kick at him, but instead of the soles aiming at his body, he instead aimed at it behind him. Several shots followed as did his signature fighting move, attacking savagely just as Ikki tried to block. He was somewhat breakdancing, but the swordsman doesn't know he still has something up on his sleeve. Just as Ikki was putting an end to his savage deadlock of breakdancing kicks, Mercury made him block his kick with his blade and pumped a shot at him from the blocked kick.

While it was similar to the beginning, this time was different.

"Take this!"

Mercury shouted as the shots that he made was currently swirling around the platform flew towards Ikki's position, who was still a bit dazed from the dirty move. Instead, he was pelleted by the shots and a recurring explosion from his shots occurred, making fumes around it. He smirked and chuckled a bit, before turning around without a single amount of respect. But the moment he looked at the screen, his jaw dropped. And the crowd grew wild as the announcers also noticed it.

 **"It would seem that even if the barrage connected, no amount of damage is seen in Ikki Kurogane's body! Not even a scratch!"** Port said with amazement.

The screen depicted Kurogane's... 'aura' to be at _its normal state_ while Mercury's was at the fifty percent. No damage occurred. After what Port said, the screen changed with what might be how the black-haired swordsman dodged his attacked. It showed frame by frame how Ikki's body blurred in every possible moment the shot would've connected. He didn't just evade it, he literally evaded it without even taking a single step away from his position!

The crowd grew wild from this, thinking that Mercury's move would end the fight. Instead it didn't.

And instead, it infuriated him... _and made him fear._

Mercury opened his near-clacking teeth, "Don't tell me... you..."

"Know that it would happen, right? I expected it since the moment you backed away," Ikki looked at his blade, "And expected it before you jumped back."

Mercury glared at him with anxiety. He knew that beforehand?

"Don't tell me... your semblance is reading minds, right?" Mercury pointed at him with a grit on his teeth.

Ikki shook his head.

"Then what is-"

 _ **"With my weakest, I'll beat your strongest!"**_

 _...?_

And with that, Ikki rushed at him with a soul-crushing glare. Right now, Mercury's mind was in a state of terror. He was arrogant, snobby of his ability. And now, his skill is nothing more but dirt to him. His own hard work to create a purely unique fighting style that even drove Pyrhha to a standstill is nothing but a mere joke to him!

 _He didn't expect him!_

"I'll show you! I'll show you!"

 _Emerald didn't expected him._

Mercury shot at him multiple times, never giving heed to Emerald's call using her power.

 _Cinder never expected him._

Ikki raised his blade and pointed it at Mercury, charging at him as the shots that should've went to his body flew past him. The crowd was in disbelief, what should've been deadly blows flew past him, as if the shots were the wind and he was the airplane's wings.

 _ **No one ever expected him!**_

" _For one to beat a genius..._ "

Ikki raised his blade up to the night sky, just before his slash would descend on Mercury.

" _One must become a **demon**._"

And then, everything became black for Mercury, as he dropped to the ground.

* * *

The crowd grew wild, cheered as he was defeated.

 _He hated it. He hated losing._

He could only look at the victor, Ikki Kurogane, as he looked around the Colosseum's wild crowd with a smile.

 _I'll kick that smug face off of you._

Mercury tried to up, but only for Kurogane to come forward.

 _What does the knight-in-black-armor want?_

The fighter looked up, only to see Kurogane brandishing his blade. What he didn't expect was for him to raise it.

 _Quick, you fucked-up body!_

He didn't have time, as the blade connected to his body.

 _..._

 _"What?"_

Mercury could only blink, as he looked around to see Kurogane to stop his blade at his head. The crowd as well were stunned. But they're not stunned by his sudden aggressiveness.

They were stunned because of what happened to Mercury.

 **"It would seem that Mercury Black himself is... quite the disabled person,"** Port commented, as Mercury realized and saw his prosthetic legs laid bare to all.

He wasn't aiming for his head, he was aiming for his legs!

"I noticed that it's impossible for you to have guns strapped on your legs. The only way to conceal one is to cut your legs, because even shortening the gun makes it weaker compared to the shots that you did."

He really did know.

"But to be fair, it was an honor to fight someone of your caliber."

Ikki said that before the medical attention as well as some guards came along. Looks like they lost because they didn't know he was there in the mix. They truly do. The attack of Beacon already failed. By now, he would've chased Emerald with a far greater success compared to those who succumbed to her Semblance. By now, Beacon was safe. By now, he wasn't. Because they lost that one opportunity to him.

And when he was carried away to the exit, he could only shut his eyes, letting the darkness consume his oncoming doom.


	2. Message

This message is dedicated to the persistent reviewers and the future of this fanfiction.

First of all, I will not make those 'stories'. I follow this subconscious rule where I will not read or write fanfiction about a fandom that I'm not in. I never indulge nor enforce myself with that. What I write is what I imagine. This place is my plug for that output. I hope you understand that sort of thinking.

Lastly, I will not make a full-fledged crossover. What I also think is that this fiction might ignite a spark for other writers to create a story for this fandom. Why I'm not doing so? Personal reasons.

And that's it. I'm not gonna sugarcoat more for the sake of word count. I like it concise. Have a nice day.


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